Born to clot: the European burden

Venous thrombosis is a common problem, predominantly afflicting people of E uropean origin. This European predisposition has been explained to some ext ent by the recent characterization of factor V Leiden, and the G20210A prot hrombin variant, Although it is clear that factor V Leiden is largely confi ned to Europeans, the world distribution of the prothrombin variant is not known. We have analysed samples from 22 different non-European countries an d shown that this prothrombin variant is very rare outside Europe: one case occurring in India. The reason for the confined distribution of these two mutations is unclear.